Manufacture of air-laid felts



Jan. 6, 1953 DUVALL 2,624,079

MANUFACTURE OF AIR-LAID FELTS Filed Aug. 16, 1949 f77/E 70 GOA/PS5 Patented Jan. 6, 1953 p I UNITED STATES PATENT OFFICE 2,624,079 mur erous or AIR-LAID FELTS Thure C. Duvall, Cloquet, Minn, assignor to Wood Conversion Company, St. Paul, Minn, a corporation of Delaware Application August 16, 1943, Serial No. ll0,610 10 Claims. (Cl. 19-155) 2 The present invention relates to forming airtherefrom onto a conveyer running through the laid f lts by deposition of fibers from suspension bottom or the chamber, there is a decided tendm air (or other gas), and in particular by gravity ency toward two-sidedness in the resulting felt.

fall in a soecalled deposition chamber. This is evident from consideration of the Brown- In the deposition of fibers from air suspension 5 lee Patent No. 2,389,025l in which wood fibers are to form felted structures, it is not as easy to injected into a chamber to form a mat in the maintain homogeneous distribution of the fibers manner previously described, with simultaneous injection of a spray of liquid binder for wetting at the point of deposition from the fluid vehicle a bonding agent. Said patent as it is in the case of aqueous suspensions of the fibers with fibers, for example, in conventional paper-makshows the introduction of an air stream at one ing machinery. There tend to be separations of end of the chamber to form an expanded trafibers into coarser and lighter fractions. Where jectory of the more confined original stream of constancy of conditions prevail in handling the fibers, centered at the bottom of the chamber air-suspensions, there may be found zones of prebetween the two ends. Material deposits in both determined location at the deposition area, in directions away from this trajectory. The char-1 which zones the formation of the felt is different, actors of the initially depositing layer and of the whether due to size of fibers, direction of deposit, finally depositing layer differ greatly and in each impact of striking, or other factor. Where a case the individual character more or less do moving mat collector is employed to traverse pends upon the nature of air currents in the these zones at a uniform rate, there may readily 2o chamber, which in turn depend upon the cham.- result a mat uniform in its variations from face bers construction, especially relative to locations to face- There maybe many layers characterof openings for venting from the chamber the istically diiferent, but. in general the facial apair which is introduced as he c yi m diu pearances are so different that such structures for the fibers. In the center of the chamber, that are called two sided in character. This term 5 is in the main trajectory, the bulk of fibers is.

therefore includes and contemplates multi layer uid clot into flakes or flocks and float out of the differences.

The present invention contemplates overcommain trajectory. In certain chambers, the back ing this general disadvantage by retaining the Wash of air carries these flocks to the inlet endand processes and equipment whi h present, th the initially deposited layer is resultingly irregdiffi m and usingthem t f a,h ,1f-ma,t ular and spotty in formation. Where there is rather than the above described whole-mat, and such an initial deposit, the chamber is comthen duplicating t prqcggs ha equipment t monly such that fines, more free of such flocks, form on the first half-mat li t inverted carry to the far end of the chamber and form half-mat whereby to prod ce 4 hq 'mat subthe finally deposited layer, which is resultingly stantially symmetrical with respect toits median more uniform in its texture and formation. plane. Eddy-currents may increase the back wash of invention may olfacgicod in many flocks to the inlet end of the chamber and result known processes f j'qitgd mats in poor formation in the initial deposit relative 120 air-suspensions f fibers, I egg forced 40 a better fOllIlEtlSlOIl in the final deposit in a, sui-t-. felting by blowing the suspension against a, felt.- ably long chamber. Where the wet deposited ing Soreen, by applying ti t Screen on mat is heavily compressed after formation and the other side of which there is an air suspension before drying, the inequalities of each of its surof fibers, by gravity fall of fibers from air-s-usface layers, and the inequalities of thickness from pension onto a collector, or combinations of top to bottom, become less evident, but as the the it being understood t t; thereis ti t density of the compressed felt is less, these replenish t suspension d ggtign t provide, a inequalities are more in evidence in presenting a process continuous in nature to form a contintwo-sidedness in quality and appearance. nous felted mat. The present invention aims to minimize the Herein the invention is mustt -g u two-sidedness in air-laid felts, and also to by reference to the gravity process. achieve other advantages in manufacture.

In the formation of air-laid felts fro fibers The invention is applicable to air-laid felts of by injecting substantially individualized 01' both mineral and vegetable fibers, its advanf med fibers in a dream; to a chamber or d se s are e o o nced in the case of wood persal in the air in the chamber, and for settling 5.5. fibers because of the inherent shortness thereof,

deposited. However, fibers wet with adhesive liq-- the resulting multiplicity of fibers per unit of weight, and the inherent curliness of the fibers with the resulting greater tendency to clot, festoon and interfelt. Consequently, the invention will be described in connection with apparatus and process for producing air-laid vegetable fiber felts.

In the accompanying drawings:

Fig. 1 represents more or less diagrammatically forming apparatus comprisingchambers of a known kind, but in a novel arrangement in accordance with the present invention.

Fig. 2 is an illustration in more or less diagrammatic form of a preferred arrangement for two adjacent forming chambers.

Fig. 3 is a perspective illustration of a mat made by the present invention, showing the several layers cut away to indicate their character.

In general, the invention comprises the provision of at least two or more deposition chambers in series, with the end chambers of the series in reverse directional relationship to a moving conveyor-collector passing through all of the series.

Thus, the kind of formation which starts the mat on the conveyor may be secured in finishing the deposition. This results in a more uniform appearance of the two faces, disregarding uniformity of quality within these two faces. Intervening chambers of the series, if any, are preferably even in number and in function symmetrically arranged with respect to the two half portions of the series when it is desired to minimize two-sidedness in structure and quality within the two faces as well as two-sidedness in appearance.

The invention may be carried out in a variety of ways, having regard to variation in the number of depositing chambers from two upwardly, and having regard for the direction of fiber injection in each chamber. There must be at least two chambers so that at the ends of a series of two or more chambers the direction of injection of the fibers may be opposed to each other, ther being in each end chamber a directional relationship to the wire which is reversed in the opposite end chamber. When there are more than two chambers in the series, it is preferred that the number be even and that they function symmetrically with respect to a line dividing the series into two half portions across the direction of operation. Where there is a pair of adjacent chambers which function in mutually reverse directions, it is preferred that the injection of fiber take place in opposed directions from a common region, and that this region be a space between the two chambers. Such a space provides for a platform area in which an operator may take charge of the injection apparatus for fiber and spray to both chambers without leaving the platform area. Another reason for providing a space between two such chambers, in which the operators platform is at a raised level with relation to the path of the conveyor, is to permit of free space over the mat passing from one chamber to the other as a station at which some operation may be performed on the mat. For example, in the case of any two chambers so arranged as to have such a station, the unfinished mat leaving one chamber and entering the other may receive, as from a roll, a web which is to be incorporated within the final mat. Such web may be a coarse scrim through which the felted structure of the mat becomes continuous, with resulting reinforcement of the mat by the scrim.

In Fig. 1 the numeral l0 designates an endless conveyer on which the mat is formed, passing over end rolls i l and I2, the conveyer leaving the roll I I passes into and through a series of depositing chambers, and then it may pass under one or more compression rolls indicated by the numeral it, thereby to compress the low density mat of the original formation to a suitable higher density. Such compression is commonly practiced to give the mat sufficient strength from felting to permit it to be couched from the forming con veyor is to another conveyer, such as the conveyer I 8 passing over end roll I? for carrying the couched mat through a treating chamber, which is commonly an oven l 8 when the mat is wet with aqueous adhesive solution. The numeral i9 designates a suitable transfer device for so moving the wet mat from the conveyer it to the oven conveyer it, such a device being described in the application of A. W. Heino, Serial No. 713,159, filed November 29, 1946, now U. S. Patent No. 2,493,194, issued January 3, 1950.

In 1 there is indicated more or less dia grammatically a series of depositingchambers, presently four in number, and designated 25, 23, 2? and 28. The chambers 25 and 26 are located and operated symmetrically with respect to the remaining chambers 27 and 28. In Fig. l the chambers 25 and 21 show injection of the fiber in one and the same direction, while chambers 25 and 28 operate in the reverse direction. As illustrated, the pair of chambers 25 and 2% discharge in opposite directions from a common space 39 between them, and the chambers 2? and 2B likewise discharge from a common region 3? between them. In the spaces all and 33 the numerals i3 and 34, respectively, designate operating platforms on which an operator (not shown) may stand to control the injection apparatus for each chamber, such apparatus in each case being designated generally by the numeral 35.

Thus, in operation of the series shown in Fig. l, the chamber 25 has a main trajectory 37 in which the bulk of its fibers deposits, there being regions 38 and 39 at the ends of the chamber outside of the main trajectory, in which there are formations different from each other and different from that in the trajectory 31. In chamber 2'! the same relationship exists in the same relation to the conveyer l0. Within the chambers 23 and 28 the same relationships exist, but the relationship of each chamber to the direction of the conveyer It is reverse from the relationships of chambers 25 and 21 to the conveyer It]. The shaded portion on the conveyer designates how the mat is built up in four separate areas of deposit as the conveyer passes through the bottoms of the series of four chambers. In chamber 25 the mat is designated 4|, this representing an integration of fibers in forming the mat. The section designated 42 between the chambers 25 and 26 is in static condition, and it exhibits a face of an incompleted mat on which some operation may be performed. The section designated 43 is another integrating section within the chamber 25. Next is a second static section 44 between chambers 26 and 2! on which some operation may be performed. Section 45 is another integrating section followed by a static section 66 and another integrating section it. The mat so formed at this point is of low density, in the case of wood fibers deposited by gravity, having a density of about to 1 lb. of dry fiber per cubic foot and very low in felted strength. The mat may be increased in density, with resulting gain in strength from felting by action of one or more of compression rolls I4 prior to egc gova transferat Hi to" the conveyer It for drying inof the conveyer 50 to provide-operating space 58" for the'conduct of other operations, as may be desired. As illustrated, there is shown a roll of scrim Sir-passing downwardly and over feed rolls the space 5% a web E53 of B to lay on mat 62 in such scrim so that when the scrim-covered mat 62 passes through chamber 55, the mat con tinues to form over the scrim so that in the end the mat 64- is substantially free from two-sided ness and has a mid-web of scrim for reinforcemerit.

The two-sidedness is substantially avoided by reason of the fact that the two chambers 53 and 55* operate directionally in opposition to each other, and as shown, the fibers are discharged from the common region 54 between the chambers. The numeral 65 designates the fiber injection apparatus available at platform 55, and the numeral 6B designates the adhesive spray devices available also from said platform 55.

It is to be understood that in Fig. 1 the injection apparatus generally designated as numeral v 36, and in Fig. 2 the injection devices 85. and 5t designate not only one. but a bank of several such devices crosswise of the web to be formed where the width of such web is so great as to render one such injection device inadequate in its lateral range.

It is to be understood that the invention is not limited to identical use of each chamber. The arrangement is flexible, permitting different kinds of material or different forming conditions to exist in the several chambers. Also, the differences may be employed in such a way as to build up a symmetrical composite mat, for example, one such as is shown in Fig. 3.

In Fig. 3 there is illustrated by way of example, a mat which has four distinct fiber layers and a reinforcing mid-web, yet the mat is a continuous felt and substantially free from twosidedness, being symmetrical with respect to the mid-web. The surface layers ii! and H may be of very high grade material, such as bleached sulfite fibers. The two inner layers l2 and 13 adjacent the scrim 14 may be of coarse or unbleached fiber material. Such a structure may be made by apparatus illustrated in Fig. 1. Chambers and 28 may be operated similarly with similar fiber to form the layers In and l l Chambers 26 and 21 may be similarly operated with the same kind of fiber, but difierent from that used in chambers 25 and 28. The space between the chambers 26 and 21 may be employed for embodying in the mat being formed a layer of scrim in the manner illustrated in Fig. 2.

Thus, it is to be understood that the invention may be employed in numerous ways and operated to advantage for the production of a variety of products not heretofore possible with the apparatus previously known. Such changes and modifications are contemplated as falling within the scope of the invention as expressed in the appended claims.

relationship wherein they discharge in I claim:

1. Apparatus for comprising a mova 'le-endless conveyer on. which fibers are deposited to buildup amat, a plurality of deposition chambers alined over said conveyer inwhich allowed to depositon the conveyer, and feeding means for each chamber to introduce fibers sus pended in air and to inject them into each-cham ber, the'end chambers having said feeding means at one end only for injecting the fibers in alinemerit withthe conveyer for dispersal therein and settling therefrom, the feeding means of the twoend chambers being arranged-to feed in opposite directions;

2. Apparatus for forming air-laid fiber felts comprising a movable endless conveyer on which fibers are deposited to build up a mat, two deposition chambers alined over said conveyer in which fibers suspended in air' are allowed to deposit on the conveyer; and feeding-means atone end only of-each chamber to introduce fibers suspended in air and to inject them into said chamberin alinement with said conveyer for dispersal therein and settling therefrom, of the two chambers being arranged to feedin opposite directions.

3. Apparatus for forming air-laid fiber felts comprising a movable endless conveyer on which fibers are deposited to build up a mat, two deposition chambers alined over said conveyer in which fibers suspended V in air are allowed to deposit on the conveyer, and feeding means at one end only of each chamber to introduce fibers suspended in air and to inject them into said chamber in alinement with said conveyer for dispersal therein and: settling therefrom, the feeding means of the two chambers being arranged to feed in opposite'directions, from a single location.

4. Apparatus for forming air-laid fiber felts comprising an endless conveyer on whichv fibers are deposited to build up a mat, two deposition chambers spaced from each other and alined over said conveyer in which fibers suspended in air are allowed to deposit on the conveyer, and feeding means at one end only of each chamber to indroduce fibers suspended in air and to inject them into said chamber in alinement with said conveyer for dispersal therein and settling therefrom, the feeding means of the two chambers being arranged to feed in opposite directions from the space between the chambers.

5. The method of forming air-laid felts which comprises injecting one or more streams of substantially individualized fibers all in the same generally horizontal direction into a settling chamber, moving an endless conveyer through said chamber in a direction generally parallel to the injected fibers for deposition of the fibers into a mat thereon and for removal of the mat from the chamber, injecting one or more streams of substantially individualized fibers into a second settling chamber all in the same generally horizontal direction but opposed to that of the first-mentioned injection and at a location to deposit fibers on said conveyer above the deposited fibers of the first-mentioned injection.

6. The method of forming air-laid felts which comprises injecting one or more streams of substantially individualized fibers all in the same generally horizontal direction into a settling chamber, moving an endless conveyer through said chamber in a direction generally opposed and parallel to the injected fibers for deposition forming air-laid, fiber" felts fibers suspended in air are the feeding meansof the fibers into a mat thereon and for removal of the mat from the chamber, injecting one or more streams of substantially individualized fibers into a second settling chamber all in the same generally horizontal direction but opposed to that of the first-mentioned injection and at a location to deposit fibers on said conveyer above the deposited fibers of the first-mentioned injection.

7. The method of forming air-laid felts which comprises depositing fibers from suspension in air at two separate areas of deposition by injecting one or more streams of substantially individualized fibers all in the same generally horizontal direction into a settling chamber, moving an endless conveyer through said chamber in a direction generally parallel to the injected fibers for deposition of the fibers into a mat thereon and for removal of the mat from the chamber, injecting one or more streams of substantially individualized fibers into a second settling chamber all in the same generally hori zontal direction but opposed to that of the firstmentioned injection and at a location to deposit fibers on said conveyer above the deposited fibers of the first-mentioned injection.

8. The method of forming air-laid felts which comprises depositing fibers from suspension in air at two separate areas of deposition by injecting one or more streams of substantially individualized fibers all in the same generally horizontal direction into a settling chamber, moving an endless conveyer through said chamber in a direction generally opposed and parallel to the injected fibers for deposition of the fibers into a mat thereon and for removal of the mat from the chamber, injecting one or more streams of substantially individualized fibers into a .sec ond settling chamber all in the same generally horizontal direction but first-mentioned injection and at a location to deposit fibers on said conveyer above the deposited fibers of the first-mentioned injection.

9. The method of forming felts from air-suspensions of fibers which comprises directing fibers in air suspension in a constant stream upon a moving collector to initiate a felted fiber opposed to that of the deposit on the collector, said stream being characterized by substantial constancy in its variations in constitution as reflected by said deposit on said collector being a half-mat having twosidedness in formation, and then depositing on said half-mat an inverted but like half-mat by directing thereon like fibers in a like air suspension in a like constant stream, in such a reverse relationship that the first deposited fibers on the collector from the first stream correspond to the last deposited fibers on the collector from the last stream, whereby the resulting mat is substantially symmetrical in formation with respec' to its median plane.

10. The method of forming a felted fiber mat substantially free from tWo-sidedness Which comprises continuously moving a collector on which the mat is formed through depositing regions separated by a reference plane of symmetry crosswise of the direction of movement, continuously depositing fibers on said collector in one region on one side of said plane in a manner to discharge from said region on said collector a felted half-mat characterized by tWo-sidedness, and continuously depositing fibers on said halfmat in the other region on the other side of said plane in a manner to form a like but inverted half-mat characterized by like two-sidedness, whereby to discharge from said second region a wholemat substantially symmetrical with respect to its mid-plane.

TI-IURE C. DUVALL.

asreasnoes cirsn The following references are of record in the die of this patent:

UNITED STATES PATENTS 

